Ergometers and bicycles have been used for a fairly long time as training appliances and/or for rehabilitation, and it is in this case expedient, during the intended use of these appliances, to measure the user's output during training and to evaluate it correspondingly. Complicated solutions for detecting the output involve evaluating the tension in a wrap-around drive, for example a chain, via which the applied force can be determined and from which, in turn, together with a measured angular speed, the output can be arrived at. Reference is made, in this regard, to DE 10 2005 052 445 A1.
Moreover, DE 37 22 728 C1 discloses what is known as an output meter for a crank mechanism of a bicycle, in which the force applied by a person is measured directly on the bottom bracket of the bicycle. The tread force is converted into an electrical signal as a result of the deformation of a suitable flexural element, on which strain gages are applied, and is transmitted by inductive transmission to a receiver connected to the bicycle frame. The tread speed is determined by means of the tread frequency. The two values, namely the tread force and the tread speed, are processed in a microcomputer on the bicycle, displayed and stored or converted into an output.
Furthermore, DE 44 35 174 C2 discloses a device for detecting the applied forces and output on a pedal crank, in particular of a bicycle, a force being determined separately, for both legs of the person applying the force, by measuring the shear strain on the crank pin or on the pedal shaft by means of strain gages arranged thereon.
Finally, it has been known for some time to measure torques of a rotary shaft, with or without a torsion bar, by means of magnetic methods known per se, for example by means of magnetostrictive torque sensors. Magnetostrictive torque sensors of this type are based on the magnetic properties of ferromagnetic materials, for example a tensile stress in the material causing an increase in a magnetic field induced in the material. By contrast, compressive stresses lead to a reduction in the induced magnetic field. A sensor coil fed with alternating current is predominantly used in order to induce the magnetic field into a ferromagnetic torque-transmitting shaft. A secondary pick-up coil or another means monitors the change in the induced magnetic field when the stresses in the shaft change with the torque. The voltage signal induced in the secondary coil is an indicator of the torque.
Thus, for example, DE 34 17 893 A1 describes an arrangement for the contactless detection or contactless measurement of mechanical stress states of machine parts, such as, for example, shafts, by means of a magnetostrictive torque sensor, a layer composed of amorphous magnetostrictive material being arranged on the shaft. Under the influence of mechanical stresses, this layer varies its magnetic permeability, so that, in turn, the inductance of a sensor which is arranged in the vicinity of this layer and comprises at least one coil, is varied. The coating may be sputtered or electrolytically applied to the shaft or be in foil form and be adhesively bonded to the shaft or welded to the latter.